Contingent upon the current CO2 climate debate and rising raw material prices for fossil fuels, the motor vehicle industry is taking care to reduce the fuel consumption of motor vehicles.
One possible way of achieving these goals is to electrify the drive train of the vehicle, to improve the efficiency chain and to regain energy. Possibilities for implementing this are start-stop vehicles, for example, hybrid vehicles, fuel cell vehicles and electric vehicles.
In comparison to the usual vehicles having internal combustion engines, current electric vehicles have clearly reduced ranges, which cover only 100 to 150 kilometers. In order to enable these current electric vehicles to travel farther, one would need a suitable infrastructure for charging, as well as a charging duration of several hours.
For this reason, high efficiency and a reduction in any energy losses would be desirable for electric vehicles. Measures are required that increase the range of the vehicle, and make possible a reduction in the storage capacity of the costly traction battery. But high energy efficiency is also of advantage for other vehicle types.
Vehicles having an electrified drive train have a traction battery. The latter has to be operated in temperature ranges that are below 40° C. As a consequence, in hot climatic zones, in such vehicles, coupling is necessary to the cooling circulation of the air conditioning system of the respective vehicle.
Newer vehicles having a start-stop function are typically equipped with electrically operated air-conditioning compressors, so that, if necessary, they are able to assure air conditioning of the passenger cell and of the traction battery, even during stops of the internal combustion engine.
Moreover, it has been suggested that a thermal storage unit be used, to cover the energy requirement of a vehicle during brief stopping phases.